Bidirectional Optical Link Protection Apparatus
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Solution Overview
Problem
Conventional protection systems for optical links carrying both upstream and downstream signals fail to detect faults effectively due to cancellation of optical power changes caused by downstream signal loss, making it difficult to calibrate thresholds and requiring expensive interleavers that restrict network reconfiguration.
Innovation Solution
A protection apparatus with a first and second port for coupling to an optical link and a further optical link, respectively, and a protection switch controlled by detectors for different wavelengths to selectively route upstream and downstream signals, allowing independent wavelength planning and simpler, cost-effective fault detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single optical link carries both upstream and downstream signals, then cost efficiency is improved by reducing fibres and components, but fault detection capability deteriorates due to cancellation of optical power changes
Solution Approach 1:
The patent segments the optical signals by wavelength, separating upstream signals (e.g., 1310nm) from downstream signals (e.g., 1550nm) using wavelength division multiplexing. This allows the detection system to selectively monitor upstream signals for faults while ignoring downstream signal power variations, resolving the cancellation problem while maintaining single-fibre operation
Solution Approach 2:
The patent introduces a wavelength-selective detector as an intermediary component that selectively detects optical signals at specific wavelengths. This mediator enables the system to distinguish between upstream and downstream signals, allowing fault detection in upstream signals without being affected by downstream signal power changes
2Device complexity
If conventional power detection is used for fault detection, then device complexity is reduced, but measurement precision deteriorates due to inability to distinguish signal directions
Solution Approach 1:
The patent changes the detection parameter from total optical power to wavelength-specific optical power. By using wavelength-selective detectors (e.g., optical filters combined with power detectors), the system maintains relative simplicity while achieving precise fault detection by monitoring only the upstream wavelength band
3Reliability
If interleavers are used to separate wavelengths for detection, then fault detection capability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces expensive interleaver components with simpler, cheaper wavelength-selective detection components such as optical filters and wavelength-specific power detectors. This substitution achieves the same wavelength separation function at lower cost and complexity, making the protection system economically viable
4Measurement precision
If interleavers are used for wavelength separation, then measurement precision is improved, but adaptability deteriorates due to restriction on network reconfiguration
Solution Approach 1:
The patent employs dynamically configurable wavelength-selective detectors that can be reconfigured to monitor different wavelength assignments. This dynamic capability allows the system to adapt to network reconfiguration and wavelength plan changes without requiring physical replacement of fixed interleaver components, thereby maintaining both precision and adaptability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables reliable and cost-effective protection of optical links carrying both upstream and downstream signals by isolating power detection from upstream reflections and allowing flexible wavelength selection, reducing component complexity and network inefficiencies.
Implementation Method 1
an optical power detector (not shown) is arranged to monitor the optical power received at the first port 16
Implementation Method 2
a protection switch 14 operable to selectively couple the third port 20 to the second port 18 instead of to the first port 16
Data Source
AI summary
According to embodiments of the present disclosure, apparatus is provided for protecting an optical link arranged to carry upstream optical signals and downstream optical signals. The apparatus comprises a first detector arranged to selectively detect a downstream optical signal received at a second port having a first wavelength and a second detector arranged to selectively detect a downstream optical signal received at the second port having a second wavelength different from the first wavelength. The apparatus further comprises control circuitry arranged to cause a protection switch to selectively couple a third port to the second port instead of to the first port based on the detecting by the first detector and the second detector. Also provided is a second apparatus for protecting the optical link. The second apparatus comprises a bypass element arranged to selectively direct at least a portion of an upstream optical signal at the first wavelength, received at a fourth port, such that a downstream optical signal at the first wavelength is transmitted from a fifth port.